As prior art technology, a fluid machine is known as shown in Japanese Patent Publication No.H9-250474. In this prior art, an expansion device and a compressor device are assembled into a single hermetically sealed casing, the expansion device converts heat energy into a rotational driving force in a Rankine cycle, and the compressor device is driven by the rotational force generated by the expansion device, to operate the refrigerating cycle.
In the above mentioned prior art, however, the rotational driving force generated at the expansion device can not be used for other purposes than driving the compressor device, because the expansion device and compressor device are integrally connected in the hermetically sealed casing. Furthermore, if the above mentioned prior art machine were installed in a motor vehicle to drive the compressor device by using the waste heat from an engine, it would not always be possible to get heat energy enough to drive the compressor device depending on running conditions of the motor vehicle. In such a case, the compressor device would not be operated, and therefore it would be a disadvantage in that air conditioning operation based on the refrigerating cycle by the compressor device may not be possible.